Filters are used in virtually all air conditioning and HVAC systems to filter out and remove a wide variety of airborne contaminates such as dust, dirt, pollen, bacteria, spores, and the like. Usually, one or more filter cartridges comprising a frame supporting a field of an appropriate filter medium is installed in a filter housing that positions the filter in the path of air flowing through the system. As air is circulated through the system, it passes through the filter medium, which collects the airborne contaminates while allowing the filtered air to pass. Periodically, such filters become so clogged with filtered matter that they begin to restrict the flow of air through the system and must be replaced. To this end, most filter cartridges are designed to be removed easily from their filter housings and replaced with a fresh cartridge.
Automobile heating and air conditioning systems are also usually provided with a replaceable filter or filters to remove airborne particles. This is particularly true of newer cars and trucks, which are often subject to regulations requiring that air be filtered as it is circulated into the cabin of the vehicle. Providing a car or truck with a filter element that is easily replaceable has proven to be a challenge, especially for passenger cars. The reason is that the filter element must be relatively expansive in surface area to accommodate the air flow of the vehicle's HVAC system. However, there usually is insufficient space under the dash of the vehicle or under the hood in some cases to provide a slot or opening in the filter housing long enough to accommodate a filter of such size.
As a solution to this space problem, auto makers have developed matable filter segments, each of which is narrow enough to be inserted into a short slot in the filter housing. These segmented filters are installed by being inserted one by one into the short slot. As each filter segment is inserted, it is pushed up manually above the position of the slot so that the next successive filter segment can be inserted into the slot. In some cases, the filter segments have edges configured to couple together as each filter segment is slid in under the previous segment. In this way, a unitary filter cartridge spanning the interior dimensions of the filter housing is progressively built up as each successive filter segment is inserted. The filter slot can then be closed for operation of the HVAC system. When it is desired to remove the filter for replacement, the slot is opened and the filter segments are progressively pulled out of the filter housing through the narrow slot, whereupon a new filter can be installed in successive segments as discussed above.
While segmented filters have proven functional in automotive HVAC systems, they have nevertheless been plagued with a variety of problems inherent in their design. First, the filters are relatively expensive to manufacture since each individual filter segment must be manufactured separately and three or more segments are required for each installation. Perhaps more problematic, however, is the inherent cumbersome and difficult procedure required to remove and replace the filter segments. In many instances, the filter housing and the filter slot therein is hidden beneath a cramped dash or under a cramped hood. As a result, a mechanic often must remove and install filter elements while lying prone on a floorboard or in some other relatively contorted position. To make matters worse, the installation of new filter elements sometimes must be done by feel in vehicles where the filter slot is not readily visible. As a result of such difficulties, it is not uncommon for less dedicated mechanics simply to remove an old clogged filter and close up the filter housing slot without installing a new filter. This leads ultimately to contamination and deterioration of the HVAC system because airborne bacteria and particles that are not filtered tend to collect on evaporators and working components of the HVAC system over time requiring a complete disassembly and cleaning.
Accordingly, there exists a need for an improved filter cartridge for installation in filter boxes located in cramped locations of vehicles. The cartridge should be inexpensive to manufacture, efficient in operation, and should be simple and easy to install, even when such installation must be accomplished by feel. It is to the provision of such a filter cartridge that the present invention is primarily directed.